Animal waste material, both liquid and solid such as manure, urine, and straw bedding material, accumulate in an animal enclosure from which they must be periodically removed. Manure pumps have become increasingly popular in the last decade or so for transferring the animal waste material from a barn to a collection area located outside the barn. The manure is stored in the collection area and taken to the fields when ready.
A typical installation of a manure pump involves installing the pumping apparatus beneath the floor of a barn and running a discharge pipe from the apparatus to the collection area, which is generally a pit dug in the ground or other suitable manure holding area. The discharge pipe is as long as necessary to transport the manure the required distance. The pump apparatus includes a hopper opening onto the floor of the barn to receive animal waste material, generally from a suitable barn cleaning apparatus; when the pump apparatus is actuated, typically once or twice a day, the waste material collected in the hopper is pumped through the discharge pipe to the collection area where it is stored for future use.
One form of animal waste pumping apparatus, as successfully sold by the assignee of the present invention for example, employs a hopper with an open bottom through which the animal waste material collects in front of a reciprocating ram or piston that is actuated to pump the waste material through the discharge pipe. The waste material does not enter into the ram or piston of this type of apparatus, which is often referred to as a "solid piston" pump. This type of pump is particularly effective with animal wastes containing a large amount of solid materials.
Another form of animal waste pumping apparatus utilizes a hollow piston through which the waste material flows during operation of the equipment. The hollow piston has an open top and/or open rear end through which the waste material collected in the hopper enters into the piston. A gate valve is associated with the piston and opens during the return stroke of the hollow piston to allow the waste material to flow through and in front of the piston; the gate valve closes during the pumping stroke of the piston so that the waste material can be pumped through the discharge piping associated with the apparatus. The hollow piston type of pump is generally considered to be advantageous for use with waste material containing a relatively large proportion of liquids. Several companies now manufacture hollow piston pumps of various constructions. U.S. patents relating to hollow piston pumps include U.S. Pat. Nos. 3,872,981, 3,687,311 and 3,981,635.
The present invention relates to a hollow piston type of animal waste pumping system and provides several features which I believe improve upon the hollow piston manure pumps presently available. The hollow piston pumps of which I am aware exhibit one or more of the following deficiencies: (1) waste materials containing large amounts of dry material such as long straw bedding can cause difficulties by plugging or blocking the entry of material into the hollow piston; (2) waste material collected in the hopper of the pump can become caked or somewhat solidified and thereby cause inefficient flow of waste material into the hollow piston; (3) while all of the pumps contain a hollow piston reciprocating with a pumping chamber, none of them provides for effective low friction movement of the piston within the chamber or effective sealing of the pump and chamber to prevent sprayback of waste material; (4) with some pumps, it is difficult to repair or replace parts associated with the hollow piston after the pump has been installed.